The invention relates to a device for an X-ray apparatus, for removing scattered radiation. Scattered radiation is removed a scatter grid which is coupled to a roller. The roller is pressed against a cam. The surface of the cam is shaped so that during a rotation of the cam, the point of contact with the roller is shifted in a direction perpendicular to the cam's shaft.
A device as described above is described in German Offenlegungsschrift No. 2,733,613. In this device, rotation of the cam causes the scatter grid to be displaced perpendicularly to the direction of its laminations in order to prevent imaging of the grid during an X-ray exposure.
The scatter grid must be displaced comparatively quickly at the beginning of each exposure because the exposure duration cannot be predicted when an automatic exposure device is used, and because imaging of the grid must be avoided even for short exposures. Since the maximum displacement of the grid (the so-called stroke) is usually limited for structural reasons in devices of this kind, the scatter grid is oscillated back and forth in many known devices in order to remove the scattered radiation. However, there is a risk that the grid laminations will be imaged when the grid reverses direction because the scatter grid becomes momentarily stationary at these reversals several times during an exposure.
In the device described in German Offenlegungsschrift No. 2,733,613 the risk of imaging the grid is eliminated by journalling the roller eccentrically on the scatter grid (or on a part which is connected thereto) so that the position where the grid reverses direction changes. However, this device requires a comparatively fast drive, so that the grid reverses direction several times during an exposure. Consequently, the X-ray apparatus may start to oscillate, thus affecting the sharpness of the X-ray image.